A large FPD, such as an organic EL display or a liquid crystal panel display, is manufactured through a process for irradiating, with ion beams, a substrate that forms a large FPD. Patent document 1 describes a known example of such a device that performs an irradiation process with ion beams. The device includes a plurality of ion sources and only transports a substrate in a transporting direction so that ion beam irradiation may be performed a number of times. In comparison with a structure that performs ion beam irradiation with a single ion source, this structure allows for versatility in the irradiation characteristics such as the dose and energy of ion beams that irradiates a substrate.